Drafting machine



March 9, 1965 e. w. SMITH DRAFTING MACHINE Filed March '7, 1960 FIG.7.

INVEN TOR. GENE W. SMITH United States Patent 3,172,206 DRAFTING MAC Gene W. Smith, 5008 La Canada Blvd, La Canada, Calif. Filed Mar. 7, 1960, Ser. No. 13,001 1 Claim. (Cl. 3379) This invention relates to a drafting machine and more particularly to an improved construction featuring an accessory fingergrip attached to the junction fitting supporting the scales of such machines and greatly facilitating the convenience, ease and accuracy of use of the machines.

Conventional drafting machines have a protractor head dominated by a large diameter control knob easily grasped in the left hand while setting the scale arms at various angles and shifting them from place to place on the drafting board. The latter operation is performed while the elbow is held pressed against the board and with the arm, wrist and finger muscles being controlled in a precise manner to shift the scale with precision to the desired new setting. Such movements tax the nervous and muscular control facilities of the draftsman excessively and this is particularly true when the machine is being used for cross-hatching or similar work requiring drawing closely spaced lines. Furthermore, the long and complicated muscular complex and multiple joints between the elbow and the fingertips through which this exacting control must be exercised throughout the working day impose a heavy burden on the draftsman.

By the present invention the foregoing and other shortcomings of conventional drafting machines are substantially elrninated without limiting the utility, efiiciency or mode of use of the machine. These objectives are accomplished by the provision of an accessory fingergrip designed for mounting on the base end of the horizontal scale without need for any change in the machine or the use of tools or special fasteners. Thus, the accessory grip is designed to have a telescoping frictional fit over the end of the horizontal scale mounting arm at a point spaced closely beside the usual control knob.

Owing to the design and position of the fingergrip close to the drafting surface, the machine is easily manipulated in an effortless manner within a limited range while the heel of the left hand rests firmly on the board in closely coupled relation to the fingers and thumb clutching the fingergrip. In consequence, the entire arm remains substantially relaxed and free of strain and relatively small effort is required to shift the scale or to hold it in a desired adjusted position while drawing a line.

Accordingly, it is a primary object of the present invention to provide an improved drafting machine having a pair of closely spaced control knobs or fingergrips selectively usable by the draftsman and each presenting its own advantages.

Another object of the invention is the provision of a drafting machine having a relatively small fingergrip anchored to the junction fitting supporting the vertical and horizontal scales and so designed and contoured as to facilitate the close and fine adjustment of the machine by the left hand while the heel of that hand remains firmly pressed against the drafting surface.

Another object of the invention is the provision of a drafting machine having a relatively large control knob comfortably fitting the palm of the left hand for manipulation of the machine while the left elbow remains pressed against the drafting surface, the machine being characterized by the provision of a supplemental fingergrip of relatively small proportions secured to the supported end of the horizontal scale and usable in the adjustment of the machine through small distances by the manipulation of the fingers while the heel of the draftsmans left hand remains firmly pressed against the drafting surface.

"ice

Another object of the invention is the provision of an accessory fingergrip adapted to be rigidly secured to the horizontal scale supporting arm of a drafting machine without need for tools or special fastening devices.

Another object of the invention is the provision of an accessory fingergrip of simple, lightweight, inexpensive design detachably assemblable over the end of the supporting arm for the horizontal scale of a drafting machine and forming a firm frictional fit therewith.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which a preferred embodiment of the invention is illustrated:

FIGURE 1 is a fragmentary plan view of a drafting machine incorporating dual control members in accordance with the present invention;

FIGURE 2 is a View taken along line 2-2 on FIGURE 1 and showing a typical operating position of the draftsmans left hand when using the fingergn'p control to manipulate the machine;

FIGURE 3 is a sectional view upon line 3--3 of FIG- URE 1;

FIGURE 4 is an inverted perspective view of the fingergrip shown in FIGURE 1;

FIGURE 5 is a perspective of another embodiment of the fingergrip, parts being broken away to show structural details;

FIGURE 6 is a transverse sectional view of an embodiment of the invention taken medially thereof and showing a spring clip mounting member for securing the grip to the scale arm; and

FIGURE 7 is a fragmentary view looking in the direction of the arrows 77 of FIGURE 6.

Referring more particularly to FIGURES 1 and 2, there is shown fragmentarily the control portion of a conventional drafting machine designated generally 10, such as that shown in the Leendert Ketting United States Patent 2,370,971, dated March 4, 1945. Drafting machines and constructions of this type are characterized by a parallelogram linkage comprising two arm assemblies pivoted together at their adjacent ends, the end of one arm assembly being provided with suitable clamping means for anchoring the same to the rear edge of a drafting board or table. The free end of the other arm assembly is provided with a head to which is rigidly connected a protractor and a junction fitting having a pair of arms at right angles to one another for supporting the usual horizontal and vertical scales of the machine. A feature of the head and protractor assembly is a clutch arranged to be operated by a large diameter control knob comfortably fitting within the palm of the draftsmans left hand and usable to shift the scales from position to position on the drafting table. Since these basic constructional details of drafting machines are so well known and since the present invention is primarily concerned with an improvement in the scale supporting and control structure, the present showing is restricted to these components and to a fragmentary showing of the second or lower arm assembly 11.

Rigidly connected to the underside of the free end of arm assembly 11 is a protractor dial 12, it being understood that the linkage embodied in the pivoting arms is effective to maintain dial 12 oriented in the same position relative to the drafting surface in all adjusted positions of the arm assemblies. Releasably clutched to the underside of protractor 12 is a clutch plate 13 fixed to a junction fitting 14 which is pivotable about the vertical axis of protractor 12 and includes a pair of arms 16 and 17 lying at right angles to one another and providing supports for a vertical scale 18 and a horizontal scale 19 respectively. Drafting scales 18 and 19 may be secured to arms 16 and 17 in any suitable manner, it being customary to construct the scales with threaded inserts-20 for seating screws 21 serving to secure mounting strips 22 to the top surface of the scales near one end. The latter are formed with upwardly flaring lateral edges adapted to be assembled endwise into snug frictional fit with a complementary shaped grooveway 24 formed lengthwise of the lower sides of arms 16 and 17.

Normally junction fitting 14 supporting scales 18 and 19 is held firmly clutched to protractor 12 by a pair of clutch control knobs 26 and 27. Control knob 26 is reciprocal radially of the protractor disc and selectively engageable with a suitably disposed series of notches or the like within the large diameter main control knob 30 co-axially of dial 12. The smaller knob 27 is threadedly seated in junction fitting 14and effective when rotated to release or to firmly engage aclutch plate 31, depending on the direction of rotation, with the rim of protractor 12 in any of an infinite number of adjusted positions about the axis of protractor 12 and control knob 30. The setting of: the scales in a desired angular adjusted position is facilitated by the provision of a graduated main scale 32divided in degrees and extending along the rim of the protractor, this scale being used in cooperation with a stationary vernier scale 33'carried by junction fitting 14. Antifriction free gliding support for the free end of arm assembly 11, protractor'12 and the attached scales 18 and 19 is provided by a polished dome-shaped member 35 secured to the underside of fitting 14 centrally beneath protractor 12.

As will be readily apparent from a consideration of FIGURE 2, the height and diameter of the conventional main control or manipulating knob 31) for drafting machine 10 is such that it is possible to control the movement and positioning of the machine while grasping the knob in the left hand and pressing the elbow against the drafting surface to provide a pivoting anchorage for the arm muscles. To avoid the undesirable consequences of this limitation and to provide fiexibility of use there is provided by the present invention a relatively small fingergrip 36 rigidly secured to the horizontal scale mounting arm 17 in any suitable manner. Preferably, fingergrip 36 is of elongated configuration having its axis generally parallel to the horizontal scale 19 and is of such size and proportion as to be readily and securely grasped between the fingers and thumb of the left hand while the heel of that hand rests firmly on the drafting surface forwardly of the fingergrip in the manner suggested by FIGURE 2.

As is shown in FIGURES 1-3, fingergrip 36 is molded in one piece from a suitable material, as for example, one of the firmer slightly resilient plastic materials. In the interest of light weight and economical use of materials,

the grip is thin-walled and of generally inverted channelshape lengthwise thereof. Its rear side walls are preferably contoured to provide comfortable seating recesses 37 for the fingertips, one end being formed with an appropriately disposed index finger seating pocket 38 and a thumb seating pocket 39.

The lower interior edges of the fingergrip side walls are formed with a pair of inwardly facing shallow grooves or channels 40, 40-shaped to grip snugly the opposite lateral edges of the horizontal scale supporting arm 17 as the fingergrip is assembled telescopically over the end of this arm. Neither tools nor fastening devices of any kind are required and the grip will remain-firmly in place indefinitely.

Since many draftsmen prefer to have fingergrip 36 located close to main control knob 30, it is necessary to cut away or notch the lower rear end portion of the grip as is indicated at 43 in FIGURE 4. This permits the left hand end of the rear edge'to be pressed along arm" 17 with its inner end overlying the junction of arm 17 with arm-16. Before leaving FIGURE 4, it shouldalso be pointed out that the lower lateral edges of the fingergrip may be cut away in part to provide integral inwardly projecting tangs 45 arranged in staggered relation relative to one another to increase the flexibility and the resilient gripping action of the plastic material with respect to the edges of arm 17. It will likewise be appreciated that various other expedients can be employed to advantage in detachably holding the fingergrip firmly anchored to arm 17.

Referring now to FIGURE 5, there is shown a second preferred embodiments of the fingergrip designated generally 36 and differing from the first described fingergrip essentially in that it is designed for manufacture by extrusion from plastic stock. Accordingly, it is free of the contoured recesses 36 and 38 for seating the fingers and thumb and is of substantially uniform cross-section throughout its length. Firm gripping by the fingers is facilitated by making the opposite lateral side walls slightly inclined to one another. The lower edges are formed with shallow grooves or channels 40', 40' designed similarly to the corresponding channels 40. 40 of the first embodiment and adapted to form a firm frictional fit with the lateral edges of arm 17. As in the first described fingergrip, the lip is cut away on its underside at 43' to permit assembly of the grip close to knob 30 if the user so wishes.

Still a third form of the fingergrip is illustrated in FIGURES 6 and 7 and is designated 36". As shown, this fingergrip is of inverted box shape and includes an integral boss 48 centrally of its interior top wall. Staked to this boss is an inverted U-shaped stiff spring mounting clip 49. This clip is formed lengthwise of its lower ends with inwardly facing channels 40" adapted to fit over the opposite lateral edges of arm 17 with a resilient highfriction press fit in such manner as to hold shoulders 44 along either inner lower edge of fingergrip 36" pressed firmly against the upper lateral corners of the scale supporting arm 17', Spring mounting clip 49 is formed of relatively stiff spring material for the dual purpose of holding the fingergrip firmly assembled to arm 17 as well as to prevent relative movement between the grip and arm 17 during use of the drafting machine. Although only a single relatively wide mounting clip 49 has been shown, it will be appreciated that two or more such clips may be spaced lengthwise of the elongated fingergrip, Likewise, a single but much wider mounting clip 49 may be employed. The FIGURE 5 and 6 construction has the advantage of being more flexible and adapted to fit over scale arms 17 having wider tolerance variations than can be accommodated by the first described embodiments.

The operation of the described drafting machine will be quite apparent from the foregoing detailed description of the construction and the structural arrangement ofthe components. The machine is characterized by the provision of a pair of differently contoured and proportioned control members which can be selectively employed advantageously to maneuver the machine over the surfaceof the drafting board. During the execution of many drafting operations, the operator will find it more convenient to employ the large diameter knob 30 to manipulate the machine in the usual manner while holding his left elbow firmly pressed against the drafting table as an'anchor point. In other drafting operations, particularly finer Work, such as cross-hatching or the execution of closely spaced parallel lines, it will be much more convenient to graspfingergrip 36 between the fingers and thumb of the left hand in the manner indicated in FIGURE 2. In this 'mode of use the fingers are arched upwardly so that the wrist may be pressed against the board as close as convenient to the lower edge of the horizontal scale 19. When so held, the easily controlled muscular system of the fingers can be utilized to shift the machine speedily and with high precision from position to position without relaxing the pressure of the wrist against the drafting table. Throughout the execution of successive drafting operations while using fingergrip 36, the forearm and upper arm are relaxed and may be moved with considerable freedom,

only the muscles of the hand proper being maintained lightly tensioned.

It will therefore be appreciated that the present invention provides a drafting machine of greatly increased versatility as well as one which can be used for long periods with ease and without appreciable strain on the operator. Not only can the invention be incorporated in drafting machines as manufactured, but the fingergrip proper, constituting a particularly important aspect of the invention, can be manufactured as an accessory readily mountable on existing drafting machines without need for any structural changes in these machines or for special fastening devices.

While the particular drafting machine herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claim.

I claim:

An accessory fingergrip for slidable and detachable mounting on a drafting machine scale arm by telescopic movement over the outer free end of said scale arm, said accessory fingergrip comprising an elongated body having a downwardly facing channel portion, a downwardly facing channel-shaped spring clip secured to said fingergrip shaped to interlock frictionally with the lateral edges of a conventional drafting machine scale arm to hold said fingergrip assembled thereon with the finger contacting surfaces of said fingergrip positioned to be firmly gripped between the thumb and fingers and with the heel of the same hand engaged with and anchored against the drawing supporting surface of the drafting machine, the legs of said body portion being cut away along portions of their lower edges to provide room for the flexing of juxtaposed portions of said spring clip,

References Cited by the Examiner UNITED STATES PATENTS 146,673 1/ 74 Haslett 3'3107 549,526 1 1/ Ottenburger 3376 1,149, 8/15 Fortune 3326 1,719,461 7/29 Bolton 161 14 2,250,709 7/41 Hummel 16-114 X 2,295,444 9/42 Woodward 161 14 X FOREIGN PATENTS 627,582 3/36 Germany.

136,764 7/52 Sweden.

247,464 12/47 Switzerland.

ISAAC LISANN, Primary Examiner.

L. R. PRINCE, Examiner. 

